id Software is best known for creating iconic first-person shooters like Doom, Quake and Wolfenstein 3D. But did you know that Nintendo's smash-hit Super Mario Bros. 3 was instrumental in the company's founding?

While working at Softdisk, now-legendary programmer John Carmack developed a technique called adaptive tile refresh that made sidescrolling games on the PC feasible. As a proof-of-concept, the future id Software crew recreated Super Mario Bros. 3 on the PC (which they completed on September 28, 1990) and sent it to Nintendo.

The hope was that Nintendo would like the idea and allow them to create an official "port" for the NES. Nintendo ultimately declined, telling the team they had no interest in expanding to the PC market and that Mario was to remain exclusively on the company's own hardware.

Undeterred, the coders went on to form id Software and created Commander Keen using Carmack's clever technique. The rest, as they say, is history.

In celebration of the 25th anniversary of Commander Keen, id Software co-founder John Romero posted a video of the team's Super Mario Bros. 3 demo. As you'll see, the background music is missing, sound effects aren't what you're used to and most of the levels are different but it's unmistakably the third installment of Super Mario Bros.

One can only wonder how the history of the Mario franchise and video games in general would have been different had Nintendo taken them up on the offer.